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The process of implementing a damage identification strategy for aerospace, civil and mechanical engineering infrastructure is referred to as structural health monitoring (SHM). Here, damage is defined as changes to the material and/or geometric properties of these systems, including changes to the boundary conditions and system connectivity, which adversely affect the system's performance. A wide variety of highly effective local non-destructive evaluation tools are available for such monitoring. However, the majority of SHM research conducted over the last 30 years has attempted to identify damage in structures on a more global basis. The past 10 years have seen a rapid increase in the amount of research related to SHM as quantified by the significant escalation in papers published on this subject. The increased interest in SHM and its associated potential for significant life-safety and economic benefits has motivated the need for this theme issue. This introduction begins with a brief history of SHM technology development. Recent research has begun to recognize that the SHM problem is fundamentally one of the statistical pattern recognition (SPR) and a paradigm to address such a problem is described in detail herein as it forms the basis for organization of this theme issue. In the process of providing the historical overview and summarizing the SPR paradigm, the subsequent articles in this theme issue are cited in an effort to show how they fit into this overview of SHM. In conclusion, technical challenges that must be addressed if SHM is to gain wider application are discussed in a general manner.

Ceramic matrix composites are the emerging material of choice for structures that will see temperatures above ~1,500 °C in hostile environments, as for example in next-generation gas turbines and hypersonic-flight applications. The safe operation of applications depends on how small cracks forming inside the material are restrained by its microstructure. As with natural tissue such as bone and seashells, the tailored microstructural complexity of ceramic matrix composites imparts them with mechanical toughness, which is essential to avoiding failure. Yet gathering three-dimensional observations of damage evolution in extreme environments has been a challenge. Using synchrotron X-ray computed microtomography, we have fully resolved sequences of microcrack damage as cracks grow under load at temperatures up to 1,750 °C. Our observations are key ingredients for the high-fidelity simulations used to compute failure risks under extreme operating conditions. Gathering information on the evolution of small cracks in ceramic matrix composites used in hostile environments such as in gas turbines and hypersonic flights has been a challenge. It is now shown that sequences of microcrack damage in ceramic composites under load at temperatures up to 1,750 °C can be fully resolved with the use of in situ synchrotron X-ray computed microtomography.

The rotary direct drive electro-hydraulic servo valve (RDDPV) is extensively employed in hydraulic systems across aerospace, automotive, and various industrial sectors owing to its remarkable precision and rapid response characteristics. The investigation of the durability life of such devices, constituting intricate amalgamations of mechanical, electrical, and hydraulic components, has perennially posed a formidable challenge. To address this challenge, our study proposes a methodology grounded in failure mechanisms to systematically quantify the durability life of RDDPV. In conjunction with finite element analysis, this study delves into the fatigue durability of the transmission mechanism and the wear durability of the slide valve—two components recognized as vulnerabilities within the RDDPV. Initially, a novel approach is proposed that integrates probability theory and fuzzy theory with the traditional Miner theory, enhancing the accuracy of fatigue life predictions for transmission mechanisms. Subsequently, a meticulous examination of the wear mechanism of the slide valve ensued, wherein we quantitatively characterized the radial wear between the valve core and sleeve using the degree of line wear. Ultimately, employing durability index calculations, the total operational life of the valve is ascertained at about 435,000 hours, thereby aligning with national standards. This research methodology not only contributes significantly to the field but also holds substantial reference value for the precise quantification of the durability life of analogous electro-hydraulic pressure servo valves.

New catheter materials for peripherally inserted central catheters (PICCs) may reduce the risk of device failure due to infectious, thrombotic, and catheter occlusion events. However, data from randomized trials comparing these catheters are lacking. We conducted a randomized, controlled, superiority trial in three Australian tertiary hospitals. Adults and children who were referred for PICC placement were assigned in a 1:1:1 ratio to receive a hydrophobic or chlorhexidine PICC or a standard polyurethane PICC and were followed for 8 weeks. The primary outcome was device failure, which was a composite of infectious (bloodstream or local) or noninfectious (thrombosis, breakage, or occlusion) complications. A total of 1098 participants underwent randomization; 365 were assigned to the hydrophobic group, 365 to the chlorhexidine group, and 368 to the standard-polyurethane group. Device failure occurred in 21 of 358 participants (5.9%) in the hydrophobic group, in 36 of 363 (9.9%) in the chlorhexidine group, and in 22 of 359 (6.1%) in the standard-polyurethane group (risk difference, hydrophobic vs. standard polyurethane, -0.2 percentage points [95% confidence interval {CI}, -3.7 to 3.2; P = 0.89]; and chlorhexidine vs. standard polyurethane, 3.8 percentage points [95% CI, -0.1 to 7.8; P = 0.06]). In the hydrophobic group as compared with the standard-polyurethane group, the odds ratio for device failure was 0.96 (95% CI, 0.51 to 1.78), and in the chlorhexidine group as compared with the standard-polyurethane group, the odds ratio was 1.71 (95% CI, 0.98 to 2.99). Complications from any cause during the period of PICC placement occurred in 77 participants (21.5%) in the hydrophobic group, in 140 (38.6%) in the chlorhexidine group, and in 78 (21.7%) in the standard-polyurethane group (odds ratio, hydrophobic vs. standard polyurethane, 0.99 [95% CI, 0.69 to 1.42]; and chlorhexidine vs. standard polyurethane, 2.35 [95% CI, 1.68 to 3.29]). No adverse events were attributable to the interventions. Among adults and children who were referred for PICC placement, the risk of device failure due to noninfectious or infectious complications was not lower with hydrophobic or chlorhexidine PICCs than with standard polyurethane PICCs. (Funded by the National Health and Medical Research Council of Australia; PICNIC Australian New Zealand Clinical Trials Registry number, ACTRN12619000022167.).

ObjectiveThe aim of the study was to evaluate the incidence of peripheral inserted central catheter (PICC) tip malposition when the catheter is inserted under real-time ultrasound (RTUS) guidance when compared with conventional landmark (CL) technique in neonates. Additional objectives were to evaluate the PICC longevity and central line associated blood stream infections (CLABSI).Study designIn this randomised controlled trial, neonates were randomised to ‘RTUS’ (n = 40) or ‘CL’ (n = 40) groups. PICC tip was placed under ultrasound guidance in lower third of superior vena cava in the RTUS group. In ‘CL’ group, PICC was inserted as calculated by anatomical landmarks.ResultsThe birth weight (1286 (926, 1662) vs. 1061 (889, 1636) g) and gestation (31.12 (3.1) vs. 31.4 (3.6) wks) were comparable among the groups. RTUS guidance during PICC insertion reduced incidence of tip malposition by 52% (67.5 vs. 32.5%; RR: 0.48; 95% CI: 0.29–0.79). The longevity of PICC and episodes of CLABSI were however similar in the two groups.ConclusionsReal-time ultrasound guidance during PICC placement reduces the incidence of tip malposition.

Carbon nanotube thin-film transistors 1 are expected to enable the fabrication of high-performance 2 , flexible 3 and transparent 4 devices using relatively simple techniques. However, as-grown nanotube networks usually contain both metallic and semiconducting nanotubes, which leads to a trade-off between charge-carrier mobility (which increases with greater metallic tube content) and on/off ratio (which decreases) 5 . Many approaches to separating metallic nanotubes from semiconducting nanotubes have been investigated 6 , 7 , 8 , 9 , 10 , 11 , but most lead to contamination and shortening of the nanotubes, thus reducing performance. Here, we report the fabrication of high-performance thin-film transistors and integrated circuits on flexible and transparent substrates using floating-catalyst chemical vapour deposition followed by a simple gas-phase filtration and transfer process. The resulting nanotube network has a well-controlled density and a unique morphology, consisting of long (~10 µm) nanotubes connected by low-resistance Y-shaped junctions. The transistors simultaneously demonstrate a mobility of 35 cm 2  V –1  s –1 and an on/off ratio of 6 × 10 6 . We also demonstrate flexible integrated circuits, including a 21-stage ring oscillator and master–slave delay flip-flops that are capable of sequential logic. Our fabrication procedure should prove to be scalable, for example, by using high-throughput printing techniques. Carbon nanotube transistors with high mobilities and high on/off ratios are demonstrated, along with flexible nanotube-based integrated circuits that are capable of sequential logic.

Wireless monitoring has emerged in recent years as a promising technology that could greatly impact the field of structural monitoring and infrastructure asset management. This paper is a summary of research efforts that have resulted in the design of numerous wireless sensing unit prototypes explicitly intended for implementation in civil structures. Wireless sensing units integrate wireless communications and mobile computing with sensors to deliver a relatively inexpensive sensor platform. A key design feature of wireless sensing units is the collocation of computational power and sensors; the tight integration of computing with a wireless sensing unit provides sensors with the opportunity to self-interrogate measurement data. In particular, there is strong interest in using wireless sensing units to build structural health monitoring systems that interrogate structural data for signs of damage. After the hardware and the software designs of wireless sensing units are completed, the Alamosa Canyon Bridge in New Mexico is utilized to validate their accuracy and reliability. To improve the ability of low-cost wireless sensing units to detect the onset of structural damage, the wireless sensing unit paradigm is extended to include the capability to command actuators and active sensors.

Fault diagnosis of mechanical equipment can effectively reduce property losses and casualties. Bearing vibration signals, as one of the effective sources of diagnostic information, are often overwhelmed by substantial environmental noise. To address this issue, we present a fault diagnosis method, CCSDRSN, which exhibits strong noise resistance. This method enhances the soft threshold function in the traditional deep residual shrinkage network, allowing it to extract useful information from the fault signal to the maximum extent, thus significantly improving diagnostic accuracy. Additionally, we have developed a novel activation function that can nonlinearly transform the time frequency map across multiple dimensions and the entire region. In pursuit of network optimization and parameter reduction, we have strategically incorporated depthwise separable convolutions, effectively replacing conventional convolutional layers. This architectural innovation streamlines the network. By verifying the effectiveness of the proposed method using Case Western Reserve University datasets, the results demonstrate that the proposed method not only possesses strong noise resistance in high noise environments but also achieves high diagnostic accuracy and good generalization performance under different load conditions.

The reactor coolant pump is a key equipment in a nuclear power plant. If the leakage exceeds a certain threshold, it may cause reactor overheating and shutdown. The reactor coolant pump leakage fault usually has two problems: corrosion and scaling. Accurately and efficiently diagnosing the leakage fault mode as early as possible and predicting its remaining useful life (RUL) are important for taking timely maintenance measures. In this paper, an integrated method is proposed. First, the cross-sectional area of the first seal is extracted as a fault indicator. The motivation is that corrosion may enlarge the cross-sectional area, and scaling may reduce the cross-sectional area. Based on the fluid mechanics theory, an integrated model with several uncertain parameters is established among the cross-sectional area, temperature, and leakage at the inlet and outlet of the first seal. In the diagnosing process, a modified change-detection method is proposed to detect the starting point of degradation. Then, the unknown parameters in the previous relation are estimated, and the degrading data before the starting point of degradation are used to diagnose the leakage fault mode. Second, a time-series model of the autoregressive integrated moving average (ARIMA) is established to predict the remaining useful life based on the degrading data after the starting point of degradation. Finally, the leakage degrading data from six reactor coolant pumps of a nuclear power plant is used to perform the leakage fault mode diagnosis and life prediction with degradation point detection error rates not exceeding 4%, fault mode diagnosis correction rates 100% and practical RUL predicting results, which proves that the proposed integrated method is accurate and efficient. The proposed integrated method combines the advantages of both the physical model diagnosis and the data-driven model diagnosis and innovatively make use of the quantity of flow from the output side of the primary pump as the monitoring indicator and the cross-sectional area as the characteristic index together to diagnose the leakage fault mode happened to the seal and predict its RUL, which can meet the needs of actual operation and maintenance to ensure a healthy and stable operation of the pump and prevent unexpected shutdowns of nuclear power plants and serious accidents.

IntroductionAround 30% of peripherally inserted central catheters (PICCs) fail from vascular, infectious or mechanical complications. Patients with cancer are at highest risk, and this increases morbidity, mortality and costs. Effective PICC dressing and securement may prevent PICC failure; however, no large randomised controlled trial (RCT) has compared alternative approaches. We designed this RCT to assess the clinical and cost-effectiveness of dressing and securements to prevent PICC failure.Methods and analysisPragmatic, multicentre, 2×2 factorial, superiority RCT of (1) dressings (chlorhexidine gluconate disc (CHG) vs no disc) and (2) securements (integrated securement dressing (ISD) vs securement device (SED)). A qualitative evaluation using a knowledge translation framework is included. Recruitment of 1240 patients will occur over 3 years with allocation concealment until randomisation by a centralised service. For the dressing hypothesis, we hypothesise CHG discs will reduce catheter-associated bloodstream infection (CABSI) compared with no CHG disc. For the securement hypothesis, we hypothesise that ISD will reduce composite PICC failure (infection (CABSI/local infection), occlusion, dislodgement or thrombosis), compared with SED. Secondary outcomes: types of PICC failure; safety; costs; dressing/securement failure; dwell time; microbial colonisation; reversible PICC complications and consumer acceptability. Relative incidence rates of CABSI and PICC failure/100 devices and/1000 PICC days (with 95% CIs) will summarise treatment impact. Kaplan-Meier survival curves (and log rank Mantel-Haenszel test) will compare outcomes over time. Secondary end points will be compared between groups using parametric/non-parametric techniques; p values <0.05 will be considered to be statistically significant.Ethics and disseminationEthical approval from Queensland Health (HREC/15/QRCH/241) and Griffith University (Ref. No. 2016/063). Results will be published.Trial registrationTrial registration number is: ACTRN12616000315415.